I have been running https://webhookrelay.com/ as I side project for the last two years and since last March it's quite profitable. Environment is highly automated, running on GKE, builds and testing on drone.io while deployments are rolled out by keel.sh, some alerting goes through Node-RED so I don't have to interfere.

Still doing full-time consulting but hopefully in the next year or two I will transition full-time to it (if it's ever needed). I do plan to hire someone for marketing or sales, maybe on contracting terms and not full-time.